This paper proposes an optical signal processing for noise deletion in the 2 Dimensional Space Code Division Multiple Access communication networks by using a type of associative memory model, called semi-orthogonal associative memory model. This signal processing has a capability of global and good noise deletion since the semi-orthgonal associative memory model is globally stable and has a good recalling capacity. Furthermore, this processing can be implemented in an all-optical system. A computer simulation on this processing has been done.
Optical amplifiers are very important devices for optical fiber communication and signal processing to compensate the attenuation of signals in optical circuits. We propose high gain optical waveguide amplifiers using rare-earth-doped garnet crystalline thin films as a alternate fiber amplifiers. In order to operate optical waveguide amplifiers near 1.55μm wavelength of the optical fiber transmission window, we have chosen active ion Er^<3+> and have fabricated slab waveguides of 0.85 at % Er^<3+>-doped YIG films on the GGG substrates by RF sputtering. In this report, the composition and crystallization of Er : YIG thin film waveguides are evaluated.
A practical 1.3 μm-band optical fiber amplifier with reliable 1.01-μm-band laser diode pump light sources and an efficient praseodymium-doped In/Ga-based fluoride fiber is presented. A praseodymium-doped In/Ga-based fluoride fiber is characterized using measurable parameters, and amplified characteristics are theoretically analyzed. Signal output power of +16.2 dBm (42 mW) is achieved for a booster pumped by four 1.01-μm-band laser diodes.
Optical wavelength separator is one of the basic elements in WDM optical communication systems. Collinear acoustooptic (AO) devices are capable of wavelength control tunably. Multiplexed optical signals can be independently controlled when the WDM interval and the frequency interval of SAWs are properly designed. This paper discusses crosstalks in guided-type collinear AO separators. Further, the wavelength separation is experimentally demonstrated with fabricated devices consisting of channel proton-exchanged waveguide and Nb_2O_5 waveguide. Mode conversion between the modes in the same polarization is performed in this device.
Recently developed Graded-Index Plastic Optical Fiber (GI-POF) is most useful candidate for next generation digital home network infrastructure because of easy handling and wideband characterisitcs. To verify the performance of optical transmission system based on GI-POF, we designed a new optical module which consists of a 650nm-band resonant cavity LED and a Si pin-PD. As a result, 500MbpsX50m transmission was successfully demonstrated with the bit error rate of less than 10E-12 and the power margin of more than 4dB, by using an emphasis circuit to compensate the frequency response of the LED. This optical module is very convenient for high speed digital interface such as IEEE1394.
A new FM optical modulation and transmission scheme was proposed for an optical video transmission system employing super wide-band AM/FM signal conversion. Two FM lasers are modulated by flequency-multiplexed AM signal with opposite polarity each other, then the two flequency-modulated lights are combined and transmitted. The proposed scheme not only simplifies the transmitter configuration, but also improves fiber transmission characteristics. Both distortion and CNR degradations due to fiber chromatic dispersion and fiber non-linearity were comfirmed experimentally to be restricted compared to the conventional scheme.
In muti-channel CATV transmission systems, non-linearity of an amplifier causes intermodulation (IM). IM distortins impair the signal in CATV transmission and degrade the BER in digital channels. This paper describes probability density function (p.d.f.) of intermodulation distortions in CATV system, and verify its suitability by measuring p.d.f. at the experimental facilities for CATV system (ACT center). As a rusult, the proposal p.d.f. suits the one of intermodulation distortions (CSO, CTB) in muti-channel CATV systems.
In SCM for CATV systems, carriers are modulated by video signals or digital data, so amplitude of multiplexed signal of these modulation signals is compressed compared with that of the carries themselves, occured to intermodulation distortion. This paper presents the analytical study for Bit Error Rate paformance of 256-QAM signal to used amplitude probability density function of the inter-modulation and thermal noise. The probability density function differs Gaussian distribution. We parformaed a theorical analysis, the results matched well with measured results of BER paformance of 256-QAM signal.